1. Field of the Invention
The present invention relates to an air-inlet controlling assembly, and more particularly to an air-inlet controlling assembly for a pneumatic tool with a plastic shell.
2. Description of Related Art
Conventional pneumatic tools always have a metal shell and a heavy weight, and are inconvenient and laborious in use. Therefore, the shell of a conventional pneumatic tool is made of plastic material to decrease the weight of the conventional pneumatic tool.
In generally, the conventional pneumatic tools are used to fasten or loosen bolts or nuts and usually have an air-inlet controlling assembly and a driving shaft.
The air-inlet controlling assembly is mounted in the conventional pneumatic tool to control the flow direction of a compressed air. The driving shaft is connected to the air-inlet controlling assembly. Then, the driving shaft can apply to fasten or loosen the bolts and the nuts by changing the flow direction of the compressed air with the air-inlet controlling assembly.
With reference to FIG. 5, a first conventional air-inlet controlling assembly has a cylinder (50), a port device (51) and a control device (52). The cylinder (50) is hollow, is mounted in a conventional pneumatic tool and has a bottom and an inlet (501). The inlet (501) is formed in the bottom of the cylinder (50). The port device (51) is mounted in the cylinder (50) and has a bottom, an annular sidewall, a through hole (512) and two discharging holes (511). The through hole (512) is formed in the bottom of the port device (51) and communicates with the inlet (501) of the cylinder (50). The discharging holes (511) are formed through the annular sidewall of the port device (51) and away from the through hole (512). The control device (52) is connected to the port device (51) and has two cavities (521).
With reference to FIG. 6, a second conventional air-inlet controlling assembly is mounted in a conventional pneumatic tool having a shell (60). The shell (60) has a chamber (61), and the second conventional air-inlet controlling assembly is mounted in the chamber (61) of the shell (60) and has a cylinder (62) and a sealing slab (63). The cylinder (62) is hollow, is mounted in the chamber (61) and has a bottom and an airtight board (621). The airtight board (621) is formed on and protruded inclinedly from the bottom of the cylinder (62) to contact with the shell (60) and has an inlet (622). The inlet (622) is formed through the airtight board (621). The sealing slab (63) is attached to the airtight board (621) and has a through hole communicated with the inlet (622).
The airtight board (621) and the sealing slab (63) are contacted closely with the shell (60) to prevent a compressed air from flowing inside the chamber (61) to damage the conventional pneumatic tool.
With reference to FIG. 7, a third conventional air-inlet controlling assembly is mounted in a conventional pneumatic tool having a shell (70). The third conventional air-inlet controlling assembly is mounted in the shell (70) and has a cylinder (80) and a control shaft (82). The cylinder (80) is mounted in the shell (70) and has a bottom and a valve (81). The valve (81) is mounted axially in the bottom of the cylinder (80) and has a through hole (811). The through hole (811) is communicated with the cylinder (80) and allows compressed air to flow into the cylinder (80). The control shaft (82) is extended through the shell (70), is connected to the cylinder (90) to change the flow direction of the compressed air.
With reference to FIG. 8, a conventional pneumatic tool (90) has a shell (91) and holds a fourth conventional air-inlet controlling assembly inside. The fourth conventional air-inlet controlling assembly is mounted in the shell (91) and has a cylinder (92) and a pushing device (93). The cylinder (92) is mounted in the shell (91) and has a bottom and a valve (921). The valve (921) is mounted in the bottom of the cylinder (92) and has two through holes (922). The through holes (922) are communicated with the cylinder (92). The pushing device (93) is mounted on the shell (91) and has two buttons (931) and a control valve (932).
The buttons (931) are connected movably to the shell (70). The control valve (932) is mounted in the shell (91), is connected to the buttons (931) and contacted with the valve (921) and has an inlet (933). When one of the buttons (931) is pushed to rotate the control valve (932), the inlet (933) will communicate with one of the through holes (922) in the valve (921) to change the flow direction of the compressed air.
However, the conventional air-inlet controlling assembly for the pneumatic tool has the following shortcomings.
1. The first and the second conventional air-inlet controlling assemblies as shown in FIGS. 5 and 6 can change the flow direction of the compressed air, but the cylinders (50,62) are respectively and directly contacted to the first conventional air-inlet controlling assembly and the plastic shell (60) and the moisture, the impurities or the oil gas contained in the compressed air will be rusted and damaged with the internal elements of the conventional pneumatic tool. Thus, the useful life of the conventional pneumatic tool is reduced due to the leakage of the compressed air. After the compressed air leaking into the chamber (61) of the shell (60), the compressed air may not control the conventional pneumatic tool precisely. In addition, the first conventional air-inlet controlling assembly and the shell (60) are made of plastic and may be affected by the temperature and can not contact with the cylinders (50,62) closely.
2. The third conventional air-inlet controlling assembly as shown in FIG. 7 can keep the compressed air from leaking into the shell (70), but a valve (81) is a necessary element for connecting the control shaft (82) with the shell (70) and the cylinder (80). This increases the cost for manufacturing the air-inlet controlling assembly.
3. Although, the forth conventional pneumatic tool (90) as shown in FIG. 8 can control the flow direction of the compressed air by pushing the buttons (931), mounting the valve (921) on the cylinder (92) is trouble and may increase the cost for manufacturing an air-inlet controlling assembly. In addition, the control valve (932) is made of plastic and may be affected by the temperature and can not contact with the valve (921) closely, then the compressed air may leak into the shell (91) from a gap between the valve (921) and the control valve (932).
The air-inlet controlling assembly for a pneumatic tool in accordance with the present invention mitigates or obviates the aforementioned problems.